1. Field of the Invention
The present invention relates to a paper conveyance apparatus, including a bulk feeding apparatus having an intermediate conveyance portion for feeding a sheet-form recording medium (paper) on which an image is to be formed to an image forming apparatus such as a copier, printing machine, facsimile apparatus, printer, or plotter.
2. Description of the Background Art
In image forming apparatuses such as copiers, printing machines, facsimile apparatuses, printers including ink jet printers, and plotters, there is typically an upper limit of several hundred sheets to the paper stacking capacity (the number of sheets of paper that can be stacked) of a paper feeding apparatus provided in the main body of the image forming apparatus. Among such image forming apparatuses, an image forming apparatus such as a printing machine, especially a stencil printing machine or offset printing machine, differs from a copier or the like in that it employs an original image plate, and is therefore suited for use in bulk printing based on a plate created from a single original. Up to several thousand sheets may be printed from a single original.
In the work required for such bulk printing or other image formation, paper may be set on the paper feeding apparatus repeatedly, but such setting work is tiresome, and to eliminate wasted work time, an operator or user (to be referred to as “user” hereafter) must perform the troublesome work of monitoring the moment at which the paper runs out. To eliminate such trouble, in recent years numerous paper feeding apparatuses which can stack and supply several thousand sheets of paper to an image forming apparatus have been proposed. These paper feeding apparatuses (bulk feeding units) are attached as an option or provided as a dedicated unit (see Japanese Unexamined Patent Application Publication H6-271104, for example).
However, the first problem with such a paper feeding apparatus is that it is a dedicated apparatus which can only be attached to certain specific models, and is therefore lacking in versatility. Secondly, when such a paper feeding apparatus is to be attached to the main body of a printing machine which is already on the market, a major operation is required, which takes time and is undesirable from a service point of view. Hence such apparatuses have not been marketed widely. Thirdly, an electric connection with the printing machine main body side is required to receive information regarding the presence of paper and the paper size (in particular the length of the paper), and the work required to establish this connection is troublesome.
In consideration of these points, bulk feeding apparatuses having an intermediate conveyance portion, which are capable of supplying large volumes of paper for image formation while connected only mechanically to an image forming apparatus such as a printing machine in an offline (non-communicable) state, have been proposed and implemented in recent years (see U.S. Pat. No. 5,441,247, for example).
The bulk feeding apparatus having an intermediate conveyance portion described in U.S. Pat. No. 5,441,247 comprises a stacking portion comprising an elevatable bulk feeding table on which at least several thousand sheets of paper are stacked, a feeding mechanism portion for extracting and feeding the paper stacked on the stacking portion one sheet at a time, and an intermediate conveyance portion for feeding the paper fed from the feeding mechanism portion to the vicinity of a feeding port faced by a main body paper feeding table of a paper feeding portion, or a main body paper feeding devicei of the paper feeding portion, on the image forming apparatus main body side. This invention relates to an apparatus for extracting cut and stacked paper (sheets of paper, also known as “cut paper”, to be referred to as “paper” hereafter) from a storage apparatus and supplying the paper in conjunction with a graphic high speed printing machine, and a method therefore. According to this invention, a portable apparatus with a large paper storage capacity can be provided at a low cost. The apparatus is capable of responding to the production capacity of recent high speed printers and copiers, and is compatible with various machine types.
Incidentally, among the various image forming apparatuses to which the bulk feeding apparatus having an intermediate conveyance portion is connected, a stencil printing machine (to be referred to as “stencil printing apparatus” hereafter) uses a large variety of paper sizes. There are typically ten paper sizes, excluding “postcard size”, in common use in stencil printing apparatuses, as will be described below. In such a stencil printing apparatus, an engraved thermal stencil master is rolled onto the outer peripheral surface of a print cylinder, also known as a printing drum, and by pressing a sheet of conveyed paper using a pressing device such as a pressure cylinder or press roller onto the outer peripheral surface of the print cylinder such that ink seeps through the porous part of the print cylinder and the perforated part of the thermal stencil master, the ink is transferred onto the paper to produce a printed image (see Japanese Unexamined Patent Application Publication 2002-2079, for example).
When the bulk feeding apparatus having an intermediate conveyance portion described in U.S. Pat. No. 5,441,247 is connected offline to the stencil printing apparatus described above in order to feed paper thereto, only a specific paper size, more specifically a paper length determined by the paper conveyance direction, can be conveyed, and hence although there is no problem when a paper conveyance system for the specific paper size is employed, the apparatus cannot be used by users of stencil printing apparatuses such as copiers in which a large variety of paper sizes is used.
In response, a novel bulk feeding apparatus having an intermediate conveyance portion which can solve this problem has been proposed in Japanese Patent Application 2003-064490, Japanese Patent Application 2003-065649, and so on.
However, even with the bulk feeding apparatus having an intermediate conveyance portion proposed in Japanese Patent Application 2003-064490, Japanese Patent Application 2003-065649, and so on, when using a large variety of paper sizes, the leading edge of the paper must be stopped in a predetermined position. More specifically, the stopping position of the leading edge of a sheet of paper conveyed from the intermediate conveyance portion must substantially match the stopping position of the leading edge of a sheet of paper set on the main body feeding table of the stencil printing apparatus or the like (corresponding to a stopping position P0 shown in FIG. 11 and a reset position serving as an initial set position). However, it was discovered that when small paper in particular is conveyed, the paper advances too far, as will be described in detail below with reference to the drawings.